People were shocked when federal prosecutors charged the owners of a motel in Oacoma, S.D., a town of fewer than 500, with keeping Philippine women in virtual slavery, forcing them to work 20-hour days under the threat of violence and taking back their paychecks after they had been endorsed to deposit in their own accounts.

Prosecutors said the enslaved women performed cleaning and front-desk duties at the motel and were expected to work second jobs at fast-food restaurants. Every aspect of their lives, according to records in the 2007 case, was controlled, including what they ate, where they lived, what they wore and to whom they spoke.

Human traffickers had crept unnoticed into the small Lyman County community, located on the west bank of the Missouri River 80 miles southeast of Pierre, the state's capital. But the townsfolk soon learned that Interstate 90, which roars right by Oacoma, is part of the "Midwest Pipeline," the superhighway used to deliver trafficking victims to cities across the country.

In November, federal prosecutors struck again in South Dakota, this time bringing sex-trafficking charges against a couple in Tea, a city of 4,600 also just off Interstate 90. They were convicted of using coercion and threats to force underage girls, some as young as 15, into prostitution.

"It was a shock to me to learn that people had been trafficked through South Dakota," said state Sen. Joni Cutler, a Sioux Falls Republican who sponsored legislation in January making human trafficking a state crime. She said South Dakotans like to think of the state as a place "where everybody knows everybody or is related."

"We don't want a quiet, rural area like South Dakota to become a place where people are trafficked," she said.

South Dakota Gov. Dennis Daugaard signed the Cutler bill into law on March 16.

Human trafficking generates billions of dollars each year in illicit profits, in the United States and globally, through the entrapment and exploitation of millions of people, mostly women and children. The growing illegal trade in human beings for sex or forced labor isn't limited to either rural outposts or the world's largest cities.

Young women have been forced into prostitution over the past year through deception, fraud, coercion, threats and physical violence in Denton County, Texas; rural Tennessee; St. Paul, Minn.; Norcross, Ga.; Memphis, Tenn.; Fremont, Calif.; Harrisburg, Pa.; New York City; Los Angeles; Honolulu; Woodbridge, Va.; Gaithersburg; Annapolis; and many other cities.

Just last week, a 36-year-old Mexican national was sentenced to 40 years in prison by a federal judge in Georgia on charges that he tricked girls into leaving their families in Mexico, beat them and forced them into more than 20 acts of prostitution a night in Atlanta. The man had promised to get them jobs in restaurants. Five co-defendants previously pleaded guilty in the case.

In Columbus, Ohio, dozens of illegal immigrants from Russia, Estonia, Belarus and Ukraine were forced to work as housekeepers and laundry workers after their passports were seized. In Buford, Ga., Nigerian women were forced to work as nannies and housekeepers after being threatened and physically abused. In Falls Church, 20 Indonesian women were sold as housekeepers after their passports were seized; some were sexually assaulted and their families were threatened.

Tougher laws

Texas state Sen. Leticia Van de Putte, San Antonio Democrat, introduced legislation this month to strengthen laws against human trafficking. She said 25 percent of the people trafficked into the United States pass through the state.

"We are trying to get at those who profit from selling our children," she said, adding that she became interested in the issue in 2004 when two runaways from Oregon - a 16 year-old-boy and his 14 year-old-sister - were forced into prostitution.

"Nobody wants to think there is human slavery in their neighborhood," she said.

Attorney General Eric H. Holder Jr. said nearly every country is affected by human trafficking, either as a source for or destination of the many victims. He told a human trafficking conference in Arlington last year that the problem was "an affront to human dignity" and warned that in the United States, "it is, unfortunately, growing."

"Human trafficking has become big business - generating billions of dollars each year through the entrapment and exploitation of millions," Mr. Holder said. "The poorest and most vulnerable among us are being robbed of basic rights to dignity, security and opportunity."

Assistant Attorney General Thomas E. Perez, who heads the Justice Department's Civil Rights Division, compared human trafficking to drug and gun smuggling in that it frequently involves complex organized-crime cartels. In October, during the 10th anniversary celebration of the passage of the Trafficking Victims Protection Act, he said, the number of prosecuted cases has risen from four in 2001 to more than 50 last year.

"We're not just bringing more cases, we're bringing cases of unprecedented scope and impact, taking on international organized criminal networks," he said. "But this work isn't about how many cases we've charged or how well we work together; it's about the human lives restored to freedom and dignity."

Nathan Wilson, creator of the Project Meridian Foundation, which seeks to assist law enforcement in identifying the traffickers and their victims, said the illegal trade in human beings for sexual exploitation or forced labor has reached epidemic proportions.

"Sex trafficking has become so widespread that no country, no race, no religion, no class and no child is immune," he said, adding that 1.6 million children younger than 18 - native and foreign born - have been caught in the sex trade in the United States. But, he said, the actual number of victims is hard to quantify because of the lengths to which traffickers go to keep their crimes hidden.

Billions in profits

The Washington, D.C.-based Polaris Project, which advocates stronger federal and state laws on human trafficking and provides help to victims, has said traffickers generate billions of dollars in profits by victimizing millions of people around the world and in the United States. It has said human trafficking is one of the fastest-growing criminal industries in the world.

With an estimated annual revenue of $32 billion, law enforcement authorities, government agencies and others have said human trafficking is tied with arms dealing as the second-largest criminal industry in the world - behind only drug smuggling.

U.S. Immigration and Customs Enforcement (ICE), the lead agency for investigating and dismantling human-trafficking organizations, has estimated that 800,000 people are trafficked into commercial-sex trade and forced-labor situations throughout the world every year.

ICE Deputy Assistant Director James C. Spero described human trafficking as "a global problem ... driven by profit." He said the agency opened 650 trafficking investigations during fiscal 2010, up from 560 in 2009 and 430 in 2008, and he is still trying to determine the scope of the trafficking problem.

"You don't know what you don't know," he said.

In a 2010 report, the State Department also said human trafficking claimed 800,000 victims every year. Earlier reports estimated that 80 percent of the victims were female and half of them were minors. The department also said in the 2010 report that 17,500 people were thought to be trafficked into the United States each year.

Secretary of State Hillary Rodham Clinton has said some Americans are trapped by abusive employers and others are held in sexual slavery and that the department has sent "a clear message to all of our countrymen and women: Human trafficking is not someone else's problem."

The report, for the first time, ranked the United States as a "Tier 1" country, meaning it fully complies with the Trafficking Victims Protection Act, but also identified it as a "source, transit and destination country" for human traffickers.

Lucrative way

The complex criminal nature of human trafficking as noted by Mr. Perez also has been reported by the Congressional Research Service, which said last year that in many parts of the world, "trafficking in money, weapons and people is largely conducted by criminal gangs or mafia groups." The research service called human trafficking a "lucrative way" for organized criminal groups to fund other illicit activities.

"In Latin America, Mexican drug cartels are increasingly involved in the trafficking of people as well as drugs," the report said. The Congressional Research Service also said the links between organized crime and terrorism may be significant, noting that the language school that provided some visas for the Sept. 11, 2001, hijackers also is reported to have provided visas for prostitutes of a human trafficking ring.

A Department of Health and Human Services fact sheet said that after drug dealing, human trafficking is tied with the illegal arms industry as the world's second-largest criminal industry and is the fastest growing.

That rapid rise is worrisome to Mr. Wilson, who said he is concerned that profits from human trafficking could be used to fund terrorists. He said trafficking profits were used to fund terrorists in Iraq and that some of the proceeds from businesses such as prostitution "may be diverted toward supporting terrorist groups."

Mr. Spero said ICE had not found any evidence that terrorists were benefiting from human trafficking, but acknowledged that any financial crime has the potential to be exploited by terrorists.

The Justice Department also has identified human trafficking as one of the threats posed by international organized-crime networks. It said in a 2010 report that global crime cartels were involved in Asian massage parlors in Massachusetts, Ukrainian criminal networks exploited janitorial service workers in Pennsylvania, and an Uzbek organized-crime ring exploited Philippine, Dominican Republic and Jamaican guest workers in 14 states.

The department said human traffickers know no boundaries or borders. It said the crimes exploit men, women and children, whether they be citizens, guest workers or illegal immigrants - extracting profit from the toil of others in farm fields, factories, strip clubs, suburban mansions, brothels and bars.

Major piece

William Carroll, a former district director for the now-defunct U.S. Immigration and Naturalization Service, said human trafficking is a "major piece of operating income for the cartels and other organized criminal organizations." He said the cartels are attracted to its lucrative nature and because it does not require a distribution system like drugs.

Justice brought 52 human trafficking cases in fiscal 2010, its largest single-year total. It noted in its latest report that human traffickers often prey on those who are poor, frequently unemployed or underemployed, and who may lack access to social safety nets.

"Victims are often lured by traffickers with false promises of good jobs and better lives, and then forced to work under brutal and inhumane conditions," the department said, noting that Somali gangs forced girls younger than 14 into prostitution in Minnesota, Tennessee and Ohio - passing them around like chattel for sex with other gang members or to paying customers.

Calling the trafficking of children for sex as "intolerable," U.S. Attorney Jerry E. Martin, whose office brought the case against the Somali gangs, said the problem is widespread and difficult to prosecute. The victims, he said, "are not likely to complain to the police."